Train control



Aug. 11, 1925. 1,549,003-

w; K. HOV-E TRAIN CONTROL Filed April 9. 1923 EPA/- Patented Aug. 11, 1925.

UNITED STATES PATENT OFFICE.

WIN'IHROP K. HOWE, OF ROCHESTER, NEW YORK, .ASSIGNOR T0 GENERAL RAILWAY SIGNAL COMPANY, OF GATES, NEW YORK, A CORPORATION OF NEW YORK.

TRAIN CONTROL.

Application filed April 9,

To all whom it may concern:

Be it known that I, ivlN'rnnor K. Hown, a citizen of the United States of America, residing at Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements in Train Controls, of which the following is a specification.

This invention relates to automatic brake applying mechanism adapted for automatic train control systems.

In providing apparatus for automatically controlling the train for train control systems, it is found expedient to provide mechanism which acts upon the usual air-brake system, preferably by making a service brake application to bring the train to a safe speed, or to a stop, in accordance with traflic conditions ahead and in response to control influences transmitted from the trackway to the moving train. The particular condi tions of trafiic ahead, or the particular method of transmitting control influences from the trackway to the vehicle, is not material to the present invention which deals mainly with the provision of means for applying the brakes. It is difficult to apply the brakes of a long train, especially if it is a freight train, properly and safely; and in making manual brake applications, it is found desir able to take into consideration the slack between cars, the condition of grade and curves in the trackway, and also the speed of the train.

One of the main reasons for making it ditiicult to stop a long freight train properly and safely is due to the inability to have the brakes on each of the following cars to be applied siimiltaneously, because of the time necessary for pressure changes to travel to the rear of the train. If there is much slack between cars, the cars near the front end will have their brakes applied and the speed considerably reduced before the cars at the rear will begin to slow down. This will cause the slack between cars to be taken up quickly and may cause the train to buckle and leave the rails. Generally speaking, with reference to applying the brakes of a long freight train, it may be said that the faster the train is running the less the danger of buckling a train by applying the brakes.

With the above and other coi'isideratiens 1923. Serial N0. 630,810.

in mind, among other things, it is proposed in the present invention to provide means which acts, when a train is to be slowed down or brought to a stop, to make a light brake application to bunch the slack, so to speak, and which then acts to make a harder brake application by further reducing brake pipe pressure so as to effectively stop the train. Further objects of this invention contemplate the provision of means to limit the reduction of brake pipe pressure from the normal running pressure at that point where further venting does not cause a harder brake application, that is, the point of equalization between the auxiliary reservoirs on the cars and the respective brake cylinders associated therewith; the provision of means to prevent the engineer from recharging the brake pipe while an automatic brake application is being effected; and also means to vary the time between the first, or bunching brake application, and the second, or effective brake application, in accordance with the speed of the train.

Further objects, advantages and characteristic features of the invention will appear as the description progresses.

In describing the invention in detail, reference will be made to the accoi'npanying drawing, which shows in a simplified and diagrammatic manner the parts of one embodiment of this invention which have been shown more with the view of making it easy to understand the invention, than with the idea of showing the precise construction preferably employed in practice.

It is assumed that the brake applying mechanism embodying this invention will be controlled electrically in some suitable manner, dependent upon receiving a control influence from the trackivay. The manner in which this control influence is transmitted, and whether it is dependenton the speed of the train, or other conditions, is immaterial and does not form a part of the present invention. The primary control for the brake applying mechanism is exerted by an elcctro-pneuniatic valve E. P. V., the coil or winding 1 of which is connected to a suitable device and source of current (not shown) which serves to deenergize this winding at the time and under the conditions it is desired to produce an automatic brake application. It should be noted that whole A. This application valve A comprises a valve chamber 3 in which is a slide valve 4 shifted by a piston 5. The chamber 3 is in communication with the main reservoir of the usual airbrake system by a pipe 6. Piston 5 has a small leakage hole 7 therein establishing communication between the valve chamber 3 and the cylindrical chamber 8 in which the piston 5 moves; A spring?) in the chamber 8 is made strong enough to overcome the frictional resistance of piston 5 and the slide valve 4, and acts to maintain the piston 5 to the left as shown under normal conditions with the same pressure on opposite sides of the piston 55. The cylindrical chamber 8 is connected by pipe 2:to a small chamber 10 in the bottom of the electro-pneumatic valve E. P. V. This chamber 10 is connected I to atmosphere through the vent port 11 when the electropneumatic valve E. r. V. is deenergized and its valve 12 is raised from its seat by the action of a spring 13, aided by the pressure in the chamber 10. The slide valve 4: controls the connections between various ports and passages in the seat of the application valve A, but these passages are more conveniently described in connection with the operation.

In the lower part of the application valve A, or as a separate device as desired, is an equalizingpiston 14: for operating a valve 15, corresponding in structure and function to the equalizing piston and valve forming part of the usual engineers brake valve, which is in practice located just below the valve seat of such engineers brake valve.

In determining the amount of reduction in brake pipe pressure to be made, it is preferred to compare volumes by allowing a predetermined volume of air at the normal brake pipe pressure to escape from a special pressure or equalizing reservoir into a closed reductionchamber at atmospheric pressure. The ratio of the volumes of these reservoirs is selected to correspond to the amount of reductionin brake pipe desired; and automatic venting of the brake pipe is arrested as soon as the pressure therein has been reduced to the point where it equals the resultant pressure inthe equalizing reservoir and the reduction chamber or chambers.

In theidrawing the equalizing or pressure reservoir, which is normally charged at brake pipe pressure to constitute a standard of comparison for determining the degree of brake pipe reduction, is designated E The reduction reservoir in the particular embodiment shown is namely, the reservoirs R and R The first reduction reservoir R is connected to the application valve A directly by pipes 17 and 18. The second reduction reservoir P is connected at the proper time to the reduction reservoir R by a pneumatically operated secondary application valve designated SA.

This secondary application valve SA has a piston chamber 20 and a valve chamber 21. These chambers are separated by a partition having' a piston rod gland 19 and a packing 22through which extends the piston rod 23 having a piston 24 thereon. This piston 24: is springpressed toward the right by a spring 25, but is normally held to the left by air pressure in the piston chamber 20. In the valve chamber 21 is a slide valve 26 operatively connected to the piston rod 23. This slide valve 26 is constructed with a cavity and ports in the usual way so as to connect the second reduction reservoir R to atmosphere under normal conditions, as shown, by the pipe 27, and to connect said reservoir R to the first reductionreservoir R by pipes 27 and 28, when the air pressure is released from the chamber 20 to a predetermined extent, depending upon the strength of the spring in said chamber 20. The piston chamber 20 is connected by a pipe 30 to a timing reservoir T, which is at times connected to a suitable feed valve, or to some other source of constant air pressure, by a pneumatically operated timing valve TV.

This timing valve TV is similarly pro vided with a piston chamber 31 and a valve chamber 32 separated by a partition provided witha packing 33 held in place by a gland 34 through which a piston rod 35 is adapted to reciprocate. The top end of this piston rod 35 has fastened thereto a piston 36 fitting in the chamber 31.. The lower end of the piston rod 35 is provided with a double poppet valve 38 adapted to seat against one or the other of two valve seats in this chamber. A pipe 40 leading from the middle portion of chamber 32 is connected to the timing reservoir T, whereas the upper part of the chamber 32 is connected by a pipe ll to a feed valve, or to some other suitable source of constant air divided into two parts,

pressure. The lowerxportion of the chem? ber '32 is connected to atmosphere by a port 42 adapted to be partially closed bya tapered plug 43 constituting what is conveniently called an adjustable orifice, and controlled by a suitable speed-responsive device G, which has been conventionally shown.

This speed-responsive device G comprises a shaft 45 suitably driven from the wheels of the vehicle and rotatably supported in bearings 46 and 47. A collar 48 is rigidly fastened to the shaft 45, and is connected to another collar 49 by pairs of links 50 having a weight 51 at their pivotal connections. A helical compression spring 52 is provided be tween these collars on the shaft as to maintain the weights 51 adjacent the shaft 45 when this shaft is stationary. The collar 49 is provided with an external groove engaged by a member 53 operatively connected to the plug 43. It will thus be seen that rotation of the shaft +15 causes the weights 51 to separate, thereby contracting the spring 52 and moving the tapered plug 43 toward the right, thereby enlarging the orifice comprising the passage between this plug and port 42.

Operation-liminnormal conditions, the electro-pneumatic valve E. P. V. is energized, thereby holding the valve 12 on its seat. Main reservoir pressure in valve chamber 3 from pipe 6 leaks through port 7 in the cylindrical chamber 8 ot' the application valve A, until the pressures on opposite sides of piston 5 are equal, whereupon the piston 5 is shifted to the left by the action of spring 9. In this normal position of the valve 4, main reservoir pressure may flow to the engineers brake valve through the pipe 56, whereby the engineer may control the pressure in the brake pipe and thereby control the brakes of the train in any manner he desires as long as the valve 4. is in its normal position. Brake pipe pressure may flow from the brake pipe B. P. through pipe 57 to the chamber below the equalizing piston l l, and also through passage 60, cavity 61, passage 62, to the chamber above said piston, and to the equalizing reservoir E through passage 63, thereby charging the equalizing reservoir to brake pipe pressure. In this normal position of the valve 4, the valve chamber 21 of the secondary application valve SA and the reduction reservoir R are both connected to atmosphere through the passage 65, cavity 66, and exhaust port 67.

It is thus seen that brake pipe pressure is present in the equalizing reservoir E and above the piston 36 of the timing valve, but atmospheric pressure only is present in the reduction reservoir R and below this piston 36. Brake pipe pressure above the piston 36, therefore, holds the valve 38 against its lower seat and connects the timing reservoir T to feed valve pressure through the pipes 40 and 41. The presence of feed valve pressure in the piston chamber 20 of the second ary application valve SA compresses the spring 25 and connects the reduction reservoir R to atmosphere. It should be noted that a port leading to atmosphere has been provided in the piston chamber 20 on the left side of the piston 24 to prevent the building up of chamber.

Assume now that suitable automatic apparatus on the traiipsleenergizes the coil 1 ot the valve E. Pf" because an automatic brake application is to be effected. The deenergization of the E. P. V. allows the escape of air to atmosphere from the chamber 8 through the pipe 2, chamber 10 and port 11, faster than this air can enter through the leakage port 7, thereby causing the pressure on the lefthand side of piston 5 to predominate and move the piston 5 to the right against the tension of the spring 9, this spring 9 being only strong enough to overcome the necessary friction to move the valve 4 toward the left. ith the valve 4 moved to the right by main reservoir pressure until it is arrested by the stop 69, the valve l blanks the passage leading to the engineers brake valve, and also blanks the passage 60 leading to the bottom of the equalizing piston 14.

Vith the passage 70 blanked, the supply of pressure from the main reservoir to the engineers brake valve is cut oil, so that the brake pipe may be vented at a moderate rate to give a service application, even though the engineers valve should at that time be in the running position, and also so that the engineer cannot prevent or forestall the am tomatic brake application by shifting the valve to the release position. The blanking of passage 60 cuts ofi' the pressure to equalizing reservoir E from the brake pipe, isolating it with a charge therein at the brakepipe pressure existing at the time of the automatic operation, thereby providing a pressure representative of the brake pipe pressure and affording a standard of comparison to determine how much reduction has to be made in order to give the desired brake application.

Also, in the brake applying position of the valve 4:, the passage 72 is connected to the passage 67 leading to atmosphere by the cavity 73, so that opening of the equalizing piston valve 15 vents the pressure in the brake pipe to atmosphere and causes a reduction in the brake pipe pressure to apply the brakes in the ordinary manner. Also, the passage 62 leading to the equalizing reservoir E is connected to the passage 65 leading to the first reduction reservoir R by the cavity 66. This connection between these two reservoirs: E and R allows the equalization of pressure between them at a pressure lower than the former brake pipe pressure, depending upon the relative volumes of said reservoirs. Such equalization also makes the pressure on opposite sides of the piston 36 equal so that the spring 39 moves the valve 36 against the upper seat, thereby cut-ting ofi' feed valve pressure from the timpressure in this part of the ing reservoir T and connecting this reservoir to atmosphere through the variable orfice 4-2. It should be noted that the feed pipe a1 is large as compared to the orifice 4:2"?423, so

that the timingreservoir does not begin ventinguntil the valve 38 is resting against the upper seat.

While the apparatus is in this condition, two changes of pressure transpire, namely :-(1.) the brake pipe pressure below the equalizing piston 1 1, which necessarily greater than the eqlmlization pressure above it, causes this piston 1% to rise, thereby unseating the valve 15 and allowing brake pipe pressure to escape through the passage 72, cavity Til and passageway 67 to atmosphere. This flow of pressure from the brake pipe continues until the pressures on. opposite sides of the equalizing piston is are the same, tl'iat is, until the brake pipe pressure has dropped to a value equal to the pressure due to equalization of equalizing reservoir E with reduction reservoir R at the same time the brake pipe is vented, as just described, pressure air is flowing from the timing reservoir T to atmosphere through the variable orifice .1-2. fitter a predetermined time of venting of the timing reservoir T, the spring oi the secondary application valve SA will be able to force the piston 24 toward the right against the reduced timing reservoir pressure, thereby connecting the reduction reservoir R to the reduction reservoir R and. the equalizing.

reservoir E, through the valve chamber 21 and pipes 17, 18 and 28, and causing a new equalization pressure depending on the ratio of the volume of chambers R and R to that of the equalizing reservoir E. v This in turn will cause a further reduction in brake pipe pressure, due to the action of the equalizing piston 1 1, ina. manner as heretofore described.

It should be noted that the time required to vent the timing reservoir to an extent to allow the piston 2 1 to move toward the right depends on the strength of the spring 25, the volume of this timing reservoir T and the size of the variable orifice 42. Consequently, these various factors may be adjusted to obtain the desired lapse of time between the two successive brake applications desired in practice for a particular speed. Likewise, the variable orifice 42 and the speed-responsive device G controlling it may be. so designed that the proper lapse of time occurs for the different speeds encountered in practice.

The brake application, as just described, is made in two stages, with an. intervening time interval, the application in the first stage being mainly to bunch the slack of the train, take up the lost motion in the brake rigging and ap ply the brake shoes to a certain extent, the second stage completing an application suitable for finally bringing the train to a stop,

After tra'liic conditions are again normal,

or the desired reduction in speed has been accomplished, the winding 1 of the E. P. V. is again energized by the operation of the train control apparatus. The energization of this winding 1 closes the valve 12 and allows pressure to build up in the cylinder 8, until the spring 9 moves the piston 5 and the valve 4t toward the left back to the normal position shown in the drawing, This movement of the valve 4: opens passage and allows the engineer to recharge the brake pipe through the pipe 56, this pipe be ing again connected to main reservoir pres sure. Likewise, this movement of the valve 4 again connects the equalizing reservoir E1 tot-he brake pipe and discharges the reduction reservoir B to atmosphere. The brake pipe pressure in the. equalizing reservoir, being greater than the atmospheric pressure in the reduction reservoir R causes the piston 36 of the timing valve TV to move to its lower position against the tension of the spring 34, thereby seating the valve 38 i on its lower seat, cutting oil the variable orifice 42 and again connecting the timing reservoir to the feed valve pressure. The feed valve pressure enters the timing reservoir T and charges it to teed valve pressure in a comparatively short time, thereby moving the piston 2d and valve 26 of the secondary application valve SA toward the left and discharging the reduction reservoir B through the pipe 27, cavity below the valve 26, through the port to atmosphere, thus restoring the apparatus to its normal POSil'. tion shown in the drawing.

In the particular embodiment of the invention shown and described, the area. of the orifice 42 through which the timing reservoir T discharges to atmosphere, is varied by the position which the plug 43. assumes in this orifice under the control of the speed responsive device G. In other words, the size of the orifice 42 is varied in accordance with the actual speed of the train at the varied to any desired extent for any desired.

variations in the actual speed throughout any desired range of speeds. For example, the plug 43 may be so shaped that at low speeds, say below 12 M. P. H., the orifice 4-2 is completely closed, so that there is no second reduction in brake pipe pressure, at least until after the very long time needed for the small leakage from the timing reservoir T, extremely difficult to avoid in devices of this character, to bring the pressure in said reservoir down low enough to the point where the spring 25 can shift the piston 24 and cut in the second reduction reservoir R Thus, at low speeds there will only be the one reduction in brake pipe pressure of an amount determined by the relative volumes of the equalizing reservoir E and the first reduction reservoir R Similarly, the-plug 43 may be so shaped that at high speeds, say above 30 M. P. H., the orifice 42 has its largest possible area and gives the shortest timing. At these high speeds, however, there will be no difference in the time interval. between the two stages of the brake pipe reduction. The shape of the plug 43 also determines how the timing shall vary for the different speeds and this variation may be uniform and directly in proportion to the speed or may vary at a greater rate at the lower speeds than at the higher speeds, or vice versa.

It should also be understood that the plug i3 and the speed-responsive device G may be omitted altogether for certain types of equipment and under certain conditions, without altering the functions or mode of operation of the remaining parts, the time interval between the two stages in brake pipe reduction in this instance being the same for all speeds. It may be explained here that one of the important features of the invention resides in automatically simulating the action of the engineer in making a service application of the brakes, particularly on freight trains, consisting in making a relatively small reduction in brake pipe pressure at first to straighten out the slack and stabilize braking conditions on the sev eral cars, so to speak, and then after a short delay, follow up the first reduction by a further reduction to bring about the desired intensity of braking, going to full equalization if necessary.\ The amount of. this first reduction is nearly uniform for different trains and different speeds; and in. designing an automatic mechanism such reduction may be selected without particular difliculty and be suitable for all conditions. The time interval between the first and se ond reduction, however, is susceptible of more variation for different trains under different speeds, provided it is sought to make this time interval the minimum. Such factors as the variation in the actual speed of the train at the time of the brake application may be taken into consideration in an automatic mechanism, as shown and described. Other factors affecting the time interval in question, such as the number of cars, the condition of the braking equipment, the grade on which the train or a part thereof is running, and the like, cannot,

however, be adequately compensated for in practical fashion by any automatic mechanism. Hence for general working conditions, a time interval of sufficient duration to take care of the average or most unfavorable conditions, as desired, can be selected for the automatic mechanism, care being taken to have this interval long enough to avoid damage to equipment and "other in jurious effects resulting from making the second reduction too soon. WVith such a compromise time interval, there may be unnecessary delay in obtaining the full service application under some conditions; and it is feasible for certain classes of equipment to leave out the refinement of varying the time interval dependenton the actual speed of the train, because the time interval selected would already have such margins to take care of other variable factors that the expense of the speed variation would not meet the approval of theuser. Such modification, consisting merely in the omission of the plug 43 and the speed governor G and being obvious, has not been illustrated.

In the construction shown and described, assume that the electro-pneumatic valve A is restored to normal and the supply of main reservoir pressure to the engineers valve is established. It at this time the engineers valve should happen to be in the running position, there would be a gradual release of the brakes. For train control purposes, however, it is considered to be undesirable to give an automatic release of the brakes following an automatic application. For one thing, the automatic application may have been necessary because the engineer was incapacitated. Also, the existence of danger necessitating the automatic application may have inducedthe engineer to jump. In any event, conditions may well exist where, after an automatic application, the brakes should be kept on and not automatically released, particularly where the automatic release would result from bringing the speed of the train below some predetermined speed limit. In the embodiment of the invention shown, the engineer of course can prevent the automatic release of the brakes, after the application valve A is restored, if he desires, by placing his valve in the lap position. It is generally preferred, however, to provide a control "for the electro-pnoumatic valve E. P. V. such that it will not be reenergized, or the application valve A restored to normal, except as a result of some positive manual action on the part of the engineer; but this and other features of the control of the clcctro-pneumatic valve E. P. V., being susceptible of wide variation in connection with this invention, have not been specifically shown.

Various adaptations and modifications of the particular structure illustrated and described may be made Without changing the functions and mode of operation characten izing the invention. Particularly, by following those features of construction well recognized in the air-brake art,the structure of the control devices SA and TV may be modified to eliminate the packings or stuffing boxes which have some practical objections, Also, instead of the separate and distinct reservoirs andpipe arrangements specifioa-lly shown, it is evident that the volumes may be obtained by chambers forming part of the same unitary apparatus.

It shouldbe understood that the particuconstruction and arrangement of parts shown and described is merely illustrative of the invention and that these parts may be considerably modified, without departing from the spirit and scope thereof; and it is therefore desired to be understood that the invention is not limited to the specific disclosures except as indicated in the appended claims.

What is desired to. be secured by Letters Patent of the United States, is

1. Brake applying mechanism for automatic train control systems comprising, means associated with the usual air brake system for efi'ecting a two stage brake application which if initiated will. first reduce the brake pipe pressure to a predetermined extent suflicient to bunch the slack between successive cars of a train and then a predetermined time there-after sufficient to allow such bunching of cars will cause a further and predetermined reduction in the brake pipe pressure, and means for initiating said means.

2. Brake applying mechanism for automatic train control systems comprising, means associated with the usual air-brake system which will cause a predetern'iined }pressure reduction inthe brake pipe when initiated and then after a predetermined lapse of time depending upon the speed of the train will cause a further predetermined reduction, and means for initiating said means.

3. Brake applying mechanism for automatic train control systems comprising, an application valve normally admitting main reservoir pressure to the usual engineefis valve and also charging a suitable chamber to existing brake pipe pressure, said valve when moved to its brake applyingposition acting to cut off main reservoir pressure from the engineers valve and to reduce the pressure in saidchamber to a predetermined extent, automatic means for causing a further predetermined reduction. in pressure of said chamber after a predetermined lapse of time following the operation of the valve, and automatic means venting the brake pipe to a pressure corresponding to that in said chamber.

a pressure reduction in said pressure reservoir, means for venting the brake pipe when the pressure therein exceeds that of the presi sure reservoir, and means for causing a further predetermined pressure reduction in said pressure reservoir after a predetermined lapse of time following the operation of said application valve.

5. Mechanism for automatically applying the brakes for train control purposes on vehicles equipped with the usual air-brake system comprising, in combination with the usual brake pipe, a pressure reservoir, a re duction reservoir, an application valve normally connecting the reduction reservoir to atmosphere and the pressure reservoir to the brake pipe, said application valve being operable to disconnect said normal connections and connect said reservoirs together, means for automatically causing a reduction in brake pipe pressure to accord with that in the pressure reservoir after the application valve has operated, a second reduction reservoir normally at atmospheric pressure, a secondary application valve for further reducing the pressure in the pressure reserupon the lapse of time and automatically controlled simultaneously with said first mentioned means for determining the time intervening between said successive stages of reduction.

7. Mechanism for auton'iatically applying the brakes of railway vehicles equipped with the usual automatic air-brake system comprising, pressure responsive apparatus for venting the brake pipe of the air-brake system to a predetermined extent in two successive stages with an intervening time interval, and means dependent uponthe speed of the train at the time of operation of said apparatus for varying said time interval.

8. Mechanism for automatically applying the brakes of railway vehicles equipped with the usual automatic air-brake system. comprising, pressure responsive means for venting the brake pipe of the air-brake system down to a predetermined pressure corresponding to that govening said means, and automatic means for varying the controlling pressure for said means in two successive stages with an intervening time interval.

9. Mechanism for automatically applying the brakes of railway vehicles equipped with the usual automatic air-lu'ake system comprising, a pressure reservoir, a pressure operated valve for venting the brake pipe of the air-brake system down to a pressure equal to that then existing in said pressure reservoir, automatic means operable to reduce the pressure in said pressure reservoir to a predetermined value in two successive stages with an intervening time interval.

10. In a system of automatic control for the air brakes of vehicles for train control purposes, the combination with the usual brake pipe, a pressure operated valve for venting the brake pipe, a reservoir supplying pressure to said valve, control means operable to reduce pressure in said reservoir in two successive stages, and timing means set into operation concurrently with the initiation of the operation of said control means for determining the interval of time between said stages.

11. In a system of automatic control for the air brakes of vehicles for train control purposes, the combination with the usual brake pipe, a pressure reservoir, a valve venting the brake pipe to atmosphere until its pressure corresponds with that then existing in said reservoir, a reduction reservoir normally at atmosphericpressure, means operable to connect the pressure reservoir to the reduction reservoir and thereby make a predetermined reduction in pressure in the pressure reservoir dependent upon the relative volumes of said reservoirs, a sec" ond reduction reservoir, and timing means automatically set into operation upon equalization of the pressures in the first reduction reservoir and the pressure reservoir for connecting the latter to the second reduction reservoir after the lapse of an interval of time.

12. Brake applying mechanism for automatic train control systems comprising, the combination with the brake pipe oi the usual air-brake system; of a pressure reservoir, a reduction reservoir and a timing reservoir; means normally connecting said pressure reservoir to the brake pipe, said reduction reservoir to atmosphere, and said timing reservoir to a source of constant air pressure; said means when actuated connecting said pressure reservoir and said reduction reservoir together to cause a reduction of pressure in the pressure reservoir, and connecting said timing reservoir to atmosphere through an adjustable orifice; and speedresponsive means for varying the area of said orifice in accordance with the speed of the train.

13. Brake applying mechanism for automatic train control systems comprising, means operable to reduce the brake pipe pressure in the usual air-brake system to a predetermined fractional part of its original value when operated, and other automatic means for further reducing the brake pipe pressure to a predetermined fractional part of the then existing pressure, said lastmentioncd means being operated a predetermined time atter said first mentioned means has been operated.

ll. 1n apparatus of the character described, the combination with a brake pipe, a pressure reservoir, a valve venting the brake pipe to a pressure equal to that in the pressure reservoir, a reduction reservoir, pressure operated means operable to connect the pressure reservoir to the reduction reservoir. and timing mechanism controlling said pressure operated means and including a reservoir and a restricted exhaust orifice having an area varying in accordance with the speed of the vehicle.

15. In air-brake controlling apparatus of the character described, the combination with a brake pipe, of automatic means venting the brake pipe to varying extents in succession with an intervening time interval sufficient to allow the slack between the cars of a train to be taken up.

16. In air-brake controlling apparatus of the character described, the combination with a brake pipe, of automatic means producing two successive reductions in brake pipe pressure of dili'crent values and spaced apart a period of time sulticient to allow the slack between the cars of a train to be taken up.

17. Brake applying mechanism for automatic train control systems comprising, the combination with the brake pipe of the usual air brake system; of a pressure reservoir, 21. reduction reservoir and a timing reservoir; means normally connecting said pressure reservoir to the brake pipe, said reduction reservoir to atmosphere and said timing reservoir to a source of constant air pressure; said means when actuated connecting said pressure reservoir and said reduction reservoir to cause a reduction in said pressure reservoir and connecting said timing reservoir through an orifice to atmosphere, and means for connecting said pressure reservoir to another reservoir when said timing reservoir is vented to a predetermined extent.

In testimony whereof I hereby aflix my signature.

VINTHROP K. HOlVE. 

